The Effect And Mechanism Study On The Removal Of P-Chlorobenzoic Acid By Catalytic Ozonation With Sludge-corncob Activated Carbon

The purpose of this study was to discuss the catalytic activity and mechanism of sludge-corncob activated carbon (SCAC) prepared from sewage sludge and corncob with ZnCl2as activation regent in the ozonation ofp-chlorobenzoic acid (p-CBA). For comparison purposes, experiments of adsorption on SCAC, single ozonation and SCAC catalytic ozonation process were conducted with p-CBA as the model organic pollutant. The influences of ozone concentration, catalyst dosage, initial concentration of p-CBA and aqueous pH were discussed, too. The effect of radical scavenger on the removal of p-CBA by catalytic ozonation with SCAC was also investigated. For study the reaction mechanism, the experiments of ozonation in the presence of SCAC, three commercial activated carbons and modified SCAC were carried out. In addition, the Rct value ([·OH]/[O3]) indicated the capacity of ozone transforming into·OH in the catalytic ozonation reactions with different catalyst,which can further confirm the main catalytic active site and mechanism for SCAC catalytic ozonation process.The results showed that BET surface area of SCAC was644.13m2·g-1, and the micropore structure and mesoporous structure were extensive. The amounts of acid and basic functional groups on SCAC were0.78mmol·g-1and0.27mmol·g-1, respectively.SCAC can significantly increase the performance of ozonation, especially in the early period of reaction. The removal efficiency of p-CBA by SCAC/O3in the first minute can reach60.2%, while26.1%with single ozonation. Under the different experimental conditions, the results showed that the catalytic oxidation ability of SCAC increased with the rise of ozone concentration and the decrease of initial concentration of p-CBA, and the catalytic effect increased with the catalyst dosage increasing in a certain range. During SCAC catalytic ozonation process, the removal efficiency of p-CBA is better under alkaline condition than that under acidic condition, inferring the process of transformation of ozone into·OH radicals would be promoted in the alkaline condition.SCAC catalytic ozonation of p-CBA was inhibited by the presence of tert-butyl alcohol (TBA), indicating that·OH was the major active material in SCAC catalytic ozonation process.The removal efficiencies of p-CBA by catalytic ozonation with SCAC, three commercial activated carbons and modified SCAC showed the basic functional group on SCAC was the main catalytic active site which could improve the catalytic reaction. Through the comparison for Rct value in different catalytic reaction, it is confirmed that SCAC has the better catalytic activity than commercial activated carbons. Moreover, the basic functional group on SCAC was the main active site in catalytic ozonation process, which can be used to enhance the aqueous ozone decomposition to·OH to remove p-CBA effectively.